Need help for tiny jquery problem

That I can't fix myself....I am not very good at js, so after trying for hours and hours I am asking for help...
This is (forked) what I need, but as soon as I put exactly this on the page it doesn't work anymore. :(
http://jsfiddle.net/MaryGr/kzk8frr2/2/
Downloaded an old jquery1.8.3, but no succes...has anybody an idea what I am doing wrong?
Mary

I think you want:

Code:

---

$('.talen a').click(function(event){
    event.preventDefault();
    $('.talen a').removeClass('aan')
    $(this).addClass('aan');
});

---

Thank you but computer says no...tried codepen, perfect!
https://codepen.io/MaryG/pen/OmjRdx
a bug on the site..?

Here is the stubborn testpage (still with very bad google-english), maybe that helps...
https://tandartsaanhetij.nl/index1.php

its working in google chrome and firefox on your testpage. for me, anyway. chrome even asks if i want to translate the page and shuts down the offer if i choose to push the english button you provided, instead, which then translates it into english / and vice-a-versa, into the other language if i push that button. perhaps you have made a change to your browsing options that is effecting it

You might have a cached version of your JS in your browser. If you are updating your JS or CSS pages try 'CTRL + SHIFT + R' before testing.